Agricultural planting and granular fertilizing implements commonly employ an air metering system to control the deposition of granular material onto a farm field. An exemplary seed metering system is described in U.S. Pat. No. 5,974,988, the disclosure of which is incorporated herein by reference.
In general, air seed metering systems include a fluted roller that feeds granular material, such as seed, fertilizer, or other chemicals, stored in a hopper to a series of equidistantly spaced seed tubes that deposit the granular materials in equally spaced rows.
Increasingly, seeding and fertilizing implements are being designed to provide greater coverage. This is typically achieved by increasing the number of seed tubes thereby increasing the overall width of the implement itself. In some circumstances however, it is not desirable to have this increased coverage width. For example, when seeding or fertilizing a narrow strip, the increased coverage provided by such wider implements can result in over-seeding and, as a result, a waste of product.
Thus, some air metering systems employ rollers that are segmented into two sections. For full coverage, both sections are rotated in tandem. For half coverage, one of the rollers is locked and thus not rotated. Typically, relatively costly bearings and clutching is needed to allow one section to rotate while preventing the other section from rotating. In addition, costly sealing is required to prevent premature corrosion of the bearing and clutching components from exposure to corrosive fertilizer and other chemicals.